1. Field of the Invention
This invention relates to aggregation pheromones of insects, particularly the nitidulid species Carpophilus hemipterus, C. lugubris, and C. freemani, and the use of these pheromones in combination with host plant volatiles to aid in insect control as, for example, in pheromone-baited traps.
2. References
Throughout this application, various publications are referenced by the name of the author and date of publication within parentheses. Full citations for these references may be found at the end of the specification, listed in alphabetical order.
3. Description of the Prior Art
Insect-produced volatiles (e.g., pheromones) and host plant odors (e.g., kairomones) may facilitate location of conspecifics for mating and orientation to acceptable host plants for feeding and oviposition. It is known that in several, but not all, insect species (e.g., bark beetles) pheromones and a few specific plant odors, such as monoterpenes, may act in synergy, each enhancing the attraction of the other (Borden, 1984).
Carpophilus hemipterus (L.) (Coleoptera: Nltidulidae) is a worldwide pest attacking agricultural commodities such as ripe and dried fruit, corn, wheat, oats, rice, beans, nuts, peanuts, cotton seed, copra, spices, sugar, honey, and other materials (Hinton, 1945). It is also able to vector microorganisms responsible for the souring of figs (Hinton, 1945) and fungi which contaminate corn and produce mycotoxins (Wicklow et al., 1988).
The dusky sap beetle, Carpophilus lugubris Murray (Coleoptera: Nitidulidae) is distributed from Brazil through Central America (Parsons, 1943) and probably throughout the United States (Sanford, 1958). It is found in ripe and decomposing fruit and vegetables (Sanford and Luckman, 1963), trees infected with oak wilt (Dorsey et al., 1953; Norris, 1953), and poultry manure (Pfeiffer and Axtell, 1980). It is probably most important as a pest of sweet corn (Connell, 1956; Sanford, 1958; Connell, 1975; Tamaki et al., 1982), and can cause large amounts of corn to be rejected at canneries (Luckman and Hibbs, 1959). In addition, it appears to be a vector of oak wilt (Dorsey et al., 1953; Norris, 1953; Appel, 1986), and mycotoxin-producing fungi that contaminate corn (Wicklow et al., 1988). Although tight-husked corn can provide some control, this may be defeated when corn earworms or other insects provide entry holes (Connell, 1956; Tamaki et al., 1982). However, in many cases these insects are able to enter the ears without assistance (Connell, 1956; Tamaki et al., 1982). The loose-husked varieties of dent (field) corn adopted in association with the use of mechanical harvesting promote ready entry sites for these insects (Connell, 1956).
Carpophilus freemani Dobson infests sweet corn (Sanford and Luckman, 1963) and corn seed and corn meal (Connell, 1975). It is a principal pest of figs (Smilanick and Ehler, 1976) and the principal vector of Ceratocystis canker of stone fruits including almonds, prunes, peaches, and apricots (Moller et al., 1969).
Field traps have been used to monitor or attempt to control these and other nitidulid species, and much research has gone into trap baits. Fermenting fig paste has been used as a trap bait for C. hemipterus (Obenauf et al., 1976}. Smilanick et al. (1978) determined that a 1:1:1 mixture of acetaldehyde, ethyl acetate, and ethanol was an even more effective bait for C. hemipterus than fig paste, but trap catches were still relatively small, given the huge beetle populations. Due to the low activity of 16 other host volatiles tested, Smilanick et al. (1978) concluded that C. hemipterus "appears to use a restricted number of olfactory stimuli to locate suitable hosts." Previously reported methods of monitoring C. lugubris have been of limited effectiveness. It is well known that these insects can be attracted by fermenting baits (Luckman and Hibbs, 1959). Specific methods include using freshly sawn oak or maple blocks in combination with vinegar and fungi (Neel et al., 1967; Dorsey and leach, 1956). However, the attractiveness of these baits varies over time due to changes in fermentative activity (Neel et al., 1967). Previously reported methods of attracting C. freemani are also of limited effectiveness. The only reported method specifically describing C. freemani attraction is that of Smilanick et al. (1978). The response of C. freemani to Smilanick's 3-component mixture appeared to be relatively poor compared to that of C. hemipterus, and not significantly different from fig paste or controls. Alm et al. (1985, 1986) demonstrated that esters such as propyl propionate and butyl acetate were effective baits for Glischrochilus quadrisignatus, another economically important nitidulid, but did not compete with banana. In nature, these chemicals exist in the host plant, are produced by microorganisms which have established on the plants, or both. Curiously, no pheromones have teen reported for nitidulid beetles, even though attractants of this type would probably be potent trap baits or additives to presently used baits. Pheromones have teen reported for a large number of other beetle species.